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The Cost Of Running Compiz

"Earlier this week we published benchmarks comparing Arch Linux
and Ubuntu. There were only a few areas where the two Linux
distributions actually performed differently with many of their
core packages being similar, but one of the areas where the results
were vastly different was with the OpenGL performance as Ubuntu
uses Compiz by default (when a supported GPU driver is detected)
where as Arch does not. This had surprised many within our forums
so we decided to carry out a number of tests with different
hardware and drivers to show off what the real performance cost is
of running Compiz as a desktop compositing manager in different
configurations.

"Even when OpenGL games and benchmarks are running full-screen,
in some configurations there still is a penalty imposed by Compiz.
Compiz does not stop itself when a game or application is running
full-screen even though you are not using any Compiz plug-ins or
desktop effects and as such, indirect rendering is still being
used. Albeit using a compositing window manager can be of some
benefit when running a full-screen OpenGL program as it can lead to
faster alt-switching and some other advantages, but for most users
running Compiz with a full-screen application is not needed and can
simply lead to a drop in performance due to the indirect rendering
and additional steps taken with the compositing window manager on
Linux."